Various types of MIS are being performed by surgeons, including laparascopy, endoscopy and arthroscopy surgery. In arthroscopy, small incisions are made at the affected joint to form portals for the insertion of instruments, including a small lens and lighting system (an arthroscope). The arthroscope is connected to a viewing device, such as a television camera to allow the surgeon to see the interior of the joint. Other instruments are inserted through other portals to perform a variety of tasks. For example, the surgical instrument may include an implement for manipulating native tissue (for example, tissue grasping, tissue cutting, bone abrading), or an implement for introducing and implanting a therapeutic device.
Typical surgical instruments used in arthroscopic procedures include rongeurs, such as the Kerrison rongeur, punch forceps, basket forceps, suction punches and cup curet, for example. Examples of arthroscopic instruments are described and illustrated in O'Connor's Textbook of Arthroscopic Surgery, 2nd ed., 1992, Chapter 19.
In many surgical settings, it is often necessary for the surgeon to make measurements between two points. Due to the confined spaces of arthroscopic surgery, measuring such distances is often quite difficult, particularly when the measurement needed is larger than the size of the incision or transverse to the direction of the incision. Arthroscopic knee surgery provides many such situations. For example, it may be helpful if a surgeon could measure the size of a defect in the meniscus of a knee, to aid in choosing the appropriate method to repair the defect.
An arthroscopic measuring device is disclosed in U.S. Pat. No. 6,427,351B1, which is incorporated by reference herein in its entirety. The device disclosed in that patent provides a handle and an extension. The extension has a distal tip for intraoperative insertion into the body through an incision. Two wires extend from a block in the handle through passageways in two separate tubes that comprise the extension. The block is connected to an actuator element. The actuator elements disclosed can be moved back and forth in a direction parallel to the longitudinal axis of the handle to move the wires out of an into the tubes. At their distal ends, the tubes diverge at a fixed angle so that the distance between the ends of the wires increases as the wires are pushed further outward and decreases as the wires are pulled back into the handle. Calibrations on the handle correspond with the distance between the ends of the wires so that the surgeon can determine one or more of the dimensions of a defect in the bone or cartilage.
Although the arthroscopic measuring device disclosed in U.S. Pat. No. 6,427,351B1 provides a useful surgical tool, operation of the actuating mechanism disclosed can be difficult for the surgeon, particularly due to friction as the wires are pushed through the divergent tube endings. In addition, use of that device may require that the surgeon use both hands to hold the handle and move the actuating mechanism. Finally, use of that device may not allow for repeatable measurements of the tissue and changes in the tissue over time.
Determining the size and location of a defect at a tissue site, such as the meniscus of the knee joint, can be useful in several arthroscopic procedures. Common surgical procedures for treating meniscal damage include tear repairs and menisectomies. A tear repair is most commonly performed when the tear is a clean longitudinal vertical lesion in the vascular red zone of the meniscus. The basic strategy is to stabilize the tear by limiting or eliminating radial separation of the faces of the tear when the meniscus is load bearing. Many devices and surgical procedures exist for repairing meniscal tears by approximating the faces of the meniscus at the tear. Examples of such devices and procedures are disclosed in the following U.S. Pat. Nos. 6,319,271; 6,306,159; 6,306,156; 6,293,961; 6,156,044; 6,152,935; 6,056,778; 5,993,475; 5,980,524; 5,702,462; 5,569,252; 5,374,268; 5,320,633; and 4,873,976.
Menisectomies involve the surgical removal of part of the meniscus. Such procedures have generally been performed in cases of radial tears, horizontal tears, vertical longitudinal tears outside the vascular zone, complex tears, or defibrillation. Although menisectomies provide immediate relief to the patient, in the long term the absence of part of the meniscus can cause cartilage wear on the condylar surface, eventually leading to arthritic conditions in the joint.
A variety of orthopaedic implants are available for treating damaged soft tissue. Orthopaedic implants for treatment of damaged menisci are disclosed in the following U.S. Pat. Nos. 6,042,610; 5,735,903; 5,681,353; 5,306,311; 5,108,438; 5,007,934; and 4,880,429.
The sizes and shapes of meniscal defects, including the gaps left following menisectomies, can vary from patient to patient. Typically, orthopaedic implants for treating such defects would be provided in a variety of sizes. To select the appropriate implant for a patient, the surgeon would typically use an arthroscopic probe to approximate the size of the defect. However, due to a large margin of error in such approximations, it is desirable to provide surgeons with a more accurate way to select the most appropriate implant for a particular defect.